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111 lines
3.4 KiB
Go
111 lines
3.4 KiB
Go
// Copyright 2017 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package uid supports generating unique IDs. Its chief purpose is to prevent
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// multiple test executions from interfering with each other, and to facilitate
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// cleanup of old entities that may remain if tests exit early.
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package uid
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import (
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"fmt"
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"regexp"
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"strconv"
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"sync"
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"time"
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)
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// A Space manages a set of unique IDs distinguished by a prefix.
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type Space struct {
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Prefix string // Prefix of UIDs. Read-only.
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Sep rune // Separates UID parts. Read-only.
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Time time.Time // Timestamp for UIDs. Read-only.
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re *regexp.Regexp
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mu sync.Mutex
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count int
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}
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// Options are optional values for a Space.
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type Options struct {
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Sep rune // Separates parts of the UID. Defaults to '-'.
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Time time.Time // Timestamp for all UIDs made with this space. Defaults to current time.
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}
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func NewSpace(prefix string, opts *Options) *Space {
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sep := '-'
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tm := time.Now().UTC()
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if opts != nil {
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if opts.Sep != 0 {
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sep = opts.Sep
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}
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if !opts.Time.IsZero() {
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tm = opts.Time
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}
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}
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re := fmt.Sprintf(`^%s%[2]c(\d{4})(\d{2})(\d{2})%[2]c(\d+)%[2]c\d+$`,
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regexp.QuoteMeta(prefix), sep)
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return &Space{
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Prefix: prefix,
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Sep: sep,
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Time: tm,
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re: regexp.MustCompile(re),
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}
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}
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// New generates a new unique ID. The ID consists of the Space's prefix, a
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// timestamp, and a counter value. All unique IDs generated in the same test
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// execution will have the same timestamp.
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//
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// Aside from the characters in the prefix, IDs contain only letters, numbers
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// and sep.
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func (s *Space) New() string {
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s.mu.Lock()
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c := s.count
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s.count++
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s.mu.Unlock()
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// Write the time as a date followed by nanoseconds from midnight of that date.
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// That makes it easier to see the approximate time of the ID when it is displayed.
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y, m, d := s.Time.Date()
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ns := s.Time.Sub(time.Date(y, m, d, 0, 0, 0, 0, time.UTC))
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// Zero-pad the counter for lexical sort order for IDs with the same timestamp.
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return fmt.Sprintf("%s%c%04d%02d%02d%c%d%c%04d",
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s.Prefix, s.Sep, y, m, d, s.Sep, ns, s.Sep, c)
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}
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// Timestamp extracts the timestamp of uid, which must have been generated by
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// s. The second return value is true on success, false if there was a problem.
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func (s *Space) Timestamp(uid string) (time.Time, bool) {
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subs := s.re.FindStringSubmatch(uid)
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if subs == nil {
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return time.Time{}, false
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}
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y, err1 := strconv.Atoi(subs[1])
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m, err2 := strconv.Atoi(subs[2])
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d, err3 := strconv.Atoi(subs[3])
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ns, err4 := strconv.Atoi(subs[4])
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if err1 != nil || err2 != nil || err3 != nil || err4 != nil {
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return time.Time{}, false
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}
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return time.Date(y, time.Month(m), d, 0, 0, 0, ns, time.UTC), true
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}
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// Older reports whether uid was created by m and has a timestamp older than
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// the current time by at least d.
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func (s *Space) Older(uid string, d time.Duration) bool {
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ts, ok := s.Timestamp(uid)
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if !ok {
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return false
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}
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return time.Since(ts) > d
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}
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